Re: Index on (fixed size) bytea value

On Tue, 2023-06-20 at 08:13 +0200, Les wrote:
> I'm aware of the TOAST, and how it works. I was referring to it ("I think that it should
> be as large as possible, without hitting the toast. ") I have designed a separate "block"
> table specifically to avoid storing binary data in the TOAST. So my plan is not going to
> involve out-of-band storage.
>
> Just to make this very clear: a record in the block table would store a block, not the
> whole file. My question is to finding the optimal block size (without hitting the toast),
> and finding the optimal hash algorithm for block de-duplication.

Then you would ALTER the column and SET STORAGE MAIN, so that it does not ever use TOAST.

The size limit for a row would then be 8kB minus page header minus row header, which
should be somewhere in the vicinity of 8140 bytes.

If you want your block size to be a power of two, the limit would be 4kB, which would waste
almost half your storage space.

Yours,
Laurenz Albe